Does not "epic" refer more to scope than length these days? There are plenty of book series that are long, but so limited in scope that no one would classify them as epic, like C.S. Lewis's books. There are better examples, I'm sure. LotR is considered epic because of the wonderfully detailed (though emotionally restrained) world Mr. Tolkien created. RJ took the genre of high fantasy, as he liked to call it, to sometimes ridiculous proportions. If I need a website to recall who in the world I am reading about and what he/she has done in book 3-6, the character list has gotten way out of control. But I'm still reading.
A novella-length poem is epic, to my way of thinking, just because it's amazing to sustain story and poetic structure for more than a few pages. Prose is different.
I agree with Whitefire: Brandon is striking a good balance between stopping to smell roses and getting on with the story. I think even better than Knife of Dreams, which felt rushed to me. There was just that one Psych. 101 moment of "role-playing" in TGS that made me cringe a bit (like when I read the words "deal with it" or "relationship" in fantasy: modernisms, I think), but other than that, the story flowed nicely for me.